I've been in Amateur Radio since 1974, and still find new and interesting things to do. I like to build, restore, and operate on the air. This blog has been running for many years, so be sure to check out "Jump to Posts on Specific Topics" in the RH column to drill down and find lots of stuff. Visit www.WB4IUY.net for the lowdown at WB4IUY. Email me at wb4iuy@gmail.com if you have any questions.
In 2017, I restored an Ameco R5K (kit version) shortwave receiver I received from my friend Joe KA9QAT. It worked pretty good, but while surfing the web I stumbled across a blurb with an update published by Ameco on Dec 13, 1967. It converts all I.F. amps to common emitter configuration, and boy does it make a difference!! Below is the R5K schematic, followed by a marked up version with the mods. I wanted to get this uploaded before I lost it forever :-)
The original R5K Restoration blog is on my site HERE...
This is a neat little shortwave receiver I acquired through my friend Joe. He picked it up in some of his trading, and it was in unknown condition when he gifted it to me. I've always had a "soft spot" for Ameco stuff, and this came from the Aerotron facility in Raleigh NC sometime in the late 1960's. Here's a few pics of it before I got started with the repairs...
Considering the age, it was in pretty good condition, and just needed some minor TLC on the cosmetics, the bigger challenges were waiting inside :-) I sat about to discover the various issue with this rig, and make repairs to get it operational. This one had been "tinkered" in a bunch, from the looks of things. It seems it was actually the R5K, which I learned from Rodger WQ9E. was a version offered as a kit with the RF stages pre-assembled. Initially, it was totally dead, due to problems in the low voltage power supply. Stuff all around the band switch area was connected to
the wrong terminals, circuits bridged together, etc. I spent a bit of
time working through the schematic and correcting all of that, replaced a
shorted 1000uF electrolytic immediately after the rectifiers, cleaned
the controls, etc...typical stuff.
I ran through the initial alignment, and got it working, more or less. The receiver was full of images
in the lower SW bands and easily overloaded when connected to my full
size 160m dipole. It's kind of odd to me that the AGC is defeated when
in the CW mode. The instructions say to run the RF gain as low as
possible when receiving CW of SSB signals.
After the first jaunt of repairs and troubleshooting, I found the following problems that still needed attention:
-
The BFO didn't work. I couldn't detect
any oscillation in the BFO circuit, but I decided I'd had enough fun
for one day and tossed in the towel.
- There were no dial lamps, I needed to figure out what it was supposed to have, but that shouldn't be too tough.
- I found an oddity with the AF gain control...even when all the way down, some
audio was still passed to the audio amp. It's as if the low side of the
volume control wasn't completely at ground potential. The low side of the
control is connected to the circuit board ground. If I short the high
side or wiper to chassis ground, I get a weird & loud AC buzz. I can
measure about .004 vdc between the metal chassis and the circuit board
ground, even though they are clearly connected together. I decided that I needed to look into
that more.
- Knobs... whew, it had one of every type knob ever made on it :-) . I've got to do something about that, and fabricate a bottom cover (missing that) for it.
I parked the radio for a while, until I could get motivated to come back to it for more work. After a bit of a break, I cam back for more fun. I'm pretty sure this was surely was a kit receiver. In addition to tracking down problems via the
schematic and finding a bunch of things being incorrectly connected, I
found an interesting problem in the BFO circuit... I was poking
around the non-functional BFO circuit, and decided to test the BFO
transistor. It was good, but for come reason I decided to verify the
transistor leads as tested on my old B&K transistor tester to the
pads on the board, and found it had been incorrectly installed in the radio. Once I
rotated the transistor so the leads corresponded with the correct pc
board connections, it worked. Yipee, one more perplexing problem solved! Now that it is "sorta working", I shot a few videos on put them on Youtube...
This is a short video of it receiving an AM shortwave broadcast around 6.5mhz...
This is a short video of it running with the BFO operating...
This is a short video of it receiving a little SSB on the 75m ham band...
This is a little video of it receiving a bit of CW on the 80m ham band...
The next time I returned to the project, I found and repaired these other issues:.
- A PCB trace was burned out on the bottom of the board from a 1000uF
filer cap that was shorted. I bridged the trace and replaced the cap...
- A tap on one of the LO coils was disconnected. That was corrected easily...
-
A 10pf cap, originally intended as the coupling cap from the antenna
port, was bridged totally across the preselector assy L101/102/103 at
the band switch. This coupled the antenna downstream of the preselector,
and the radio was all noise.
- A 5v reg had blown and another
was tacked in under the board. I connected it correctly, but left it on
the bottom of the board. I need to move it topside where it's supposed
to be, but that's a non-issue right now.
- It goes without saying that the entire alignment was totally jacked up I found the instruction and service info on the web and went through a complete alignment. Wow, that made a huge difference!
- No dial lamps for whatever reason, just empty sockets. Easy fix. I located some bayonet style lamps in the shop and got those installed.
-
I couldn't turn the volume down below a fairly loud level. I checked
and the lo side of the pot was at ground, made no sense. After a quick
measurement, it became clear what the problem was... The 5k volume pot
wiper wouldn't go below 300 ohms when totally CCW. Weird, I have never seen that happen in over 40 years of repairing radio gear. I replaced the
pot and all was OK.
- Cleaned all controls & band switch
- I sorta found better knobs and replaced the goofy collection of knobs... Surprisingly enough, most of the knobs I found were a decent match to photos of the radio I found online. I'm still going to wath for a junker for those, but for now, I'm pretty happy.
- I repaired a problem with the BFO adjustment coil and repaired that, and found a small knob for the BFO coil shaft.
A pic of the receiver RF stages where I found several parts in the wrong place, stuff bridged over, and some wiring totally incorrect.
Burned trace on the board, low voltage regulator tacked in on the bottom of the board incorrectly, and other goofiness :-)
Knobs switched, front panel cleaned up, and looking much better!
Here's a few pics of the nearly completed radio, less the bottom cover that I have to cut and fit, next. It plays well, and is a fun little shortwave receiver. It was originally designed to possibly be paired with a simple transmitter for ham radio use, but it really wouldn't make a good station receiver for CW or SSB, though it does perform well on AM.
Here's an advertisement by Allied Radio from 1969 for the Ameco R5 Receiver, from the 1969 Allied Radio Catalog...
Lastly, here are a few more videos of the completed unit...
- Receiving a SW station around 4mhz
- Receiving some SSB on the 75m ham band, around 3650 khz
- Receiving Radio Havana Cuba at 5040 khz
This was a fun project, and a great little SWL radio to have in the shack. Thanks to my friend Joe for this great find and awesome gift!
